Use of a pane as a protective pane

Abstract

The invention relates to the use of a pane of borosilicate glass as a protective pane, in particular as an outer protective pane, of a vehicle.

Description

[0001] The present invention relates to the use of a pane as a protective pane, in particular as an outer protective pane, of a vehicle, wherein the pane comprises borosilicate glass or consists of borosilicate glass.

[0002] A key aspect in the use and therefore also in the manufacture of vehicles is their fuel efficiency. A key element in improving this efficiency is the concept of lightweight construction. Sometimes, well-known, cost-effective materials are replaced by new materials that, although initially more expensive, offer better usability than the replaced materials due to their lower weight and associated higher fuel efficiency. For example, it is known that not only the mass-produced soda-lime glass but also the specialty glass borosilicate glass is used for vehicle glazing.

[0003] A vehicle's exterior glazing, especially its windshield, must be sufficiently durable to withstand the forces caused by wind. The trend toward ever larger windshields, in particular, requires even greater strength. This is another reason why borosilicate glass has proven itself superior to soda-lime glass.

[0004] Borosilicate glass is a type of glass containing boron oxide. It has a low coefficient of thermal expansion and high resistance to chemicals, especially acid and water resistance. It is widely used in the manufacture of light bulbs, laboratory glassware, and cookware.

[0005] Today, windshields are widely used as composites with an outer pane of 2.1 mm to 8 mm, an inner pane of 0.6 mm to 4 mm and a plastic intermediate layer of approximately 0.3 to 1.25 mm.

[0006] The chemical resistance requirements of a vehicle's exterior protective glass are very high to ensure road safety. Depending on the latitude and season, they are exposed to a wide range of weather conditions, from a wide temperature range to varying humidity, including fog and various types of precipitation such as rain, hail, and snow. They are also exposed to a wide variety of other environmental influences, such as acid rain and bird droppings.

[0007] If signs of wear appear on the windshield due to these influences, this leads to impaired visibility and even the need to replace the windshield, which incurs costs due to material consumption, labor, and downtime.

[0008] It is therefore the object of the invention to improve this situation.

[0009] This is achieved by using a pane as a protective pane, in particular as an outer protective pane, of a vehicle, wherein the pane comprises or is made of borosilicate glass and has a water resistance according to DIN ISO 719 / 720 of class 1 and an acid resistance according to DIN 12116:2001-03 of class 1 and passes the bird droppings simulation test.

[0010] In this way, the aforementioned signs of wear are reduced. In particular, scuffing or discoloration (so-called staining) that occurs due to chemical-physical attack through glass corrosion or cracking as a result of stone or hail impact, precipitation components, bird droppings, insects and their hemolymph, fungi and lichens, or adhesions that occur on surface changes that are not visible to the naked eye are reduced.

[0011] According to the disclosure, "passing the bird droppings simulation test" is understood here to mean that after conducting bird droppings simulation tests with exposure to ten cycles of light and dark time at 200x magnification, no microscopically visible roughening of the glass surface, i.e., no glass corrosion, is visible and no deposits remain.

[0012] The bird droppings simulation test involves the following test: A mixture of finely powdered 16.8 g of uric acid (7,9-dihydro-1H-purine-2,6,8(3H)-trione; CAS No. 69-93-2) is mixed with isotonic saline solution (9 g / l NaCl in water) to a paste-like consistency. 5 g of dried and sterilized natural pigeon droppings, namely excrement from Columba livia f. domestica that is at least ten days old, are added to the paste. A portion of 0.3 cm3 of this paste is applied to the plate to be tested in such a way that the contact area forms a circle with a diameter of approximately 2 cm. After one day of air drying at room temperature and 60% relative humidity, the prepared plates are subjected to UV / temperature exposure.

[0013] The described exposure is based on the environmental impact test MIL810G (based on Method 505.5, Procedure 2 (steady state test (4.4.3): 8 h approx. 2000 W / m 2< , +49 °C + 16 h 0 W / m 2< , RT). The UV / temperature exposure is carried out in cycles. One cycle consists of 8 hours of exposure, carried out with 340-380 nm black light (OSRAM HQV, 125 W), followed by 16 hours of darkness, both at temperatures between 20 °C and 50 °C.

[0014] In each cycle, after switching off the light exposure for the following hours of darkness, the spot is re-moistened with 0.1 ml of distilled water.

[0015] After a standard cleaning with a commercially available glass cleaner based on a surfactant-containing aqueous-ethanolic solution and a commercially available cellulose cloth, the sample is examined under the microscope.

[0016] The bird droppings test simulates the effect of uncleaned dirt on a vehicle window when exposed to sunlight for several days and remoistened by dew overnight. The number of cycles serving as the pass criterion takes into account the quite common case where, for example, precipitation requires several days for a natural cleaning effect. The fibers and mucilage contained in natural bird droppings are achieved by adding pigeon droppings to the uric acid / water mixture, which binds uric acid, the main glass-corrosive component of the dirt, and promotes adhesion to the glass pane. The high proportion of uric acid in the test droppings mixture simulates the aggressive excretions of, for example, seabirds.

[0017] The term vehicle is understood independently of the medium in which it moves.

[0018] A vehicle is understood to mean, in particular, a land vehicle, in particular a road-bound vehicle such as preferably a truck or passenger vehicle regardless of the drive, preferably with electric or hybrid drive, or a rail vehicle such as preferably a railway or tram car.

[0019] The protective screen can in particular be a windscreen, side window, rear window or roof window.

[0020] It can have different formats depending on the respective application, e.g. between 1500 mm 2< × 800 mm 2< or 2500 mm 2< × 1500 mm 2< or, in particular for panoramic roofs, more than 2500 mm 2< × 3000 mm 2<.

[0021] It preferably has a thickness between 0.5 mm and 7.5 mm, preferably a thickness between 1 mm and 4 mm, particularly preferably a thickness between 1.75 mm and 3 mm.

[0022] According to the invention, the pane is used as a protective pane because it protects the space enclosed by the vehicle from external influences.

[0023] It is preferably used as an outer protective screen. In this case, it is accompanied by one or more additional screens, preferably glass screens, that are closer to the space enclosed by the vehicle. The outer protective screen is closest to the space enclosed by the vehicle.

[0024] Such a pane composite is usually designed as a laminate with one or more, preferably polymeric, intermediate layers.

[0025] Preferably, a pane is used which not only has acid resistance according to DIN 12116:2001-03 of class 1, but whose leaching within class 1 is at most 0.35 mg / dm 2<, preferably at most 0.325 mg / dm 2<, particularly preferably at most 0.275 mg / dm 2<, which therefore has a particularly high acid resistance.

[0026] Preferably, a pane is used which not only has a water resistance according to DIN ISO 719 / 720 Class 1, but whose leaching within Class 1 is at most 5 µg / g Na 2 O, preferably at most 4.5 µg / g Na 2 O, which therefore has a particularly high water resistance.

[0027] Preferably, a pane is used which has a basis weight (d1) of less than 2.25 kg / m 2< , preferably at most 2.23 kg / m 2< .

[0028] The basis weight is the ratio of mass to area of a layer or sheet. The SI unit of basis weight is kg / m². This value is therefore not standardized to a specific thickness, but is simply standardized to the area per square meter of the respective object, regardless of the thickness. This specification is common for thin products such as paper or cardboard. The basis weight specification is therefore used to compare products with very similar thicknesses.

[0029] For glass panes whose thicknesses can vary over a wide range, such information is not helpful. Even within a single application, such as architectural glazing or automotive glazing, glass with very different thicknesses is used.

[0030] Therefore, in this disclosure, a "basis weight (dx)" is used for a specified thickness d = x mm.

[0031] The low surface weight described above is particularly important for vehicle windows, since the energy required to move them depends on the weight.

[0032] The low surface weight described is particularly important for large glazings, as the weight savings are then particularly noticeable compared to panes with higher surface weights.

[0033] The low basis weight described above is particularly advantageous when more than one of these panes with a low basis weight is present in a pane assembly.

[0034] Preferably, a disk is used which has an expansion coefficient CTE20-300 between 2.5 × 10 -6< / K and 5.5 × 10 -6< / K, preferably between 2.7 × 10 -6< / K and 5.2 × 10 -6< / K, particularly preferably between 3.0 × 10 -6< / K and 5.0 × 10 -6< / K, most preferably (3.3 ± 0.1) × 10 -6< / K.

[0035] Preferably, a disc is used which in wt.% oxide basis SiO 2 70 - 87 B 2 O 3 7 - 25 Na 2 O + K 2 O 0.5 - 9 Al 2 O 3 0 - 7 CaO 0 - 3 MgO 0 - 2 or SiO 2 70 - 86 Al 2 O 3 0 - 5 B 2 O 3 9.0 - 25 Na 2 O 0.5 - 5.0 K 2 O 0 - 1.0 Li 2 0 0 - 1.0 or SiO 2 78.3 - 81.0 B 2 O 3 9.0 - 13.0 Al 2 O 3 3.5 - 5.3 Na 2 O 3.5 - 6.5 K 2 O 0 - 2.0 CaO 0 - 2.0.

[0036] A glass pane as used here according to the disclosure can be produced in a process for producing a glass pane, in particular a process for continuously producing a glass pane comprising the steps Providing a mixture comprising glass raw materials, melting the mixture to obtain a glass melt, adjusting the viscosity of the glass melt, transferring the glass melt into a device for hot forming, in particular by drawing, preferably floating, hot forming the glass, in particular drawing, preferably floating, to form a glass ribbon, separating the hot-formed glass ribbon to obtain a glass pane.

[0037] Float processes are generally characterized by the addition of molten glass to molten metal, drawing it into a glass ribbon, and cooling it. Tin melt is typically used as the molten metal. To prevent oxidation of the liquid tin, the float bath is operated in a reducing protective gas atmosphere, preferably a forming gas mixture of N 2 and H 2. A slight overpressure prevails in the float bath to prevent the ingress of air and thus oxygen. The float bath thus has a virtually O 2 -free atmosphere.

[0038] Glass sheets produced using a float process therefore have two distinguishable sides: a first side (the "tin side") that was in contact with the metal bath, and a second side (the "atmosphere side") that was in contact with the forming gas atmosphere.

[0039] Glass panes produced using a float process can be distinguished from glass panes produced using other drawing processes, for example, by the fact that small residues of tin remain in a very thin surface layer on the float bath side of the pane.

[0040] If the hot forming process is a float process, an O2-containing atmosphere is preferably provided in the area downstream of the hot forming process, for example, in the dross box and / or the annealing furnace. By supplying an SO2-containing gas stream, the atmosphere at one or more points on the upper side of the glass ribbon has a higher SO2 concentration than on the tin bath side. Such a process is known from DE 10 2014 203 564 A1, but has not yet been used for borosilicate glasses.

[0041] The invention is further explained by means of examples: A set of at least 20 discs made of borosilicate glass according to the disclosure was subjected to the bird droppings simulation test: A mixture of finely powdered 16.8 g of uric acid (7,9-dihydro-1H-purine-2,6,8(3H)-trione; CAS No. 69-93-2) was mixed with isotonic saline solution (9 g / l NaCl in water) to a paste-like consistency. 5 g of dried and sterilized natural pigeon droppings, namely excretions of Columba livia f. domestica that were at least 10 days old, were added to the paste. 0.3 cm3 of this paste was applied to each of the discs to be tested, half on the tin side and the other half on the atmospheric side, in such a way that the contact area formed a circle of approximately 2 cm in diameter. After one day of air drying at room temperature and 60 The prepared panels were subjected to UV / temperature exposure at 10% relative humidity. This exposure occurred in cycles.

[0042] After each UV / temperature exposure cycle, which consisted of 8 hours of exposure using an OSRAM HQV 125W lamp, followed by 16 hours of darkness, both at room temperature. After each cycle, the spot was re-moistened with 0.1 ml of distilled water after the exposure was switched off for the following hours of darkness. One pane with the sample on the tin side and one pane with the sample on the atmospheric side were subjected to standard cleaning using a commercially available glass cleaner and a commercially available cellulose tissue and examined under a microscope at 200× magnification. The panes cleaned and examined in this way did not participate in subsequent cycles.

[0043] Both the borosilicate glass panes tested on the tin side and those tested on the atmospheric side showed no roughening of the glass surface visible microscopically at 200x magnification, i.e. no glass corrosion, and no deposits remained, even after ten cycles of light and dark.

[0044] The fact that the pane used according to this invention shows such high resistance in the bird droppings simulation test is all the more surprising since the test not only places high demands on resistance to water and acids, but goes beyond this due to its irradiation conditions and since, for example, the alkali resistance of silicate glasses, including conventional borosilicate glasses, is always less pronounced.

[0045] This makes it ideal as a protective screen, especially as an external protective screen, for a vehicle.

[0046] The bird droppings simulation test under the conditions described above was also carried out with soda-lime glass panes: After just five cycles, more than five so-called staining points of 0.05 mm² each appeared within the contact surface of both the soda-lime glass panes tested on the atmosphere side and the tin side.

[0047] Staining points are defined as non-cleanable, point-like attacks on the glass surface with a diameter of two µm or more.

[0048] In addition to the bird droppings simulation test, a bird droppings test without uric acid was conducted. Floated borosilicate glass discs and floated soda-lime glass discs were used. 5 g of dried and sterilized natural pigeon droppings, namely Columba livia f. domestica droppings at least ten days old, were mixed with 5 ml of distilled water. A 0.3 cm3 portion of this paste was applied to each disc to be tested, forming a circle with a diameter of approximately 2 cm.

[0049] After one day of air drying at room temperature and 60% relative humidity, the prepared panels were subjected to UV / temperature exposure. This occurred in cycles similar to the bird droppings simulation test. After each cycle, one panel of borosilicate glass and one panel of soda-lime glass with a sample on the tin side, and one panel of borosilicate glass and one panel of soda-lime glass with a sample on the atmospheric side, were subjected to standard cleaning using a commercially available glass cleaner and a commercially available cellulose tissue and examined under a microscope at 200x magnification. The panels cleaned and examined in this way were not subjected to further cycles.

[0050] After two cycles, more than ten so-called staining points of 1 mm2 each appeared within the contact surface of the soda-lime glass panes tested on the tin side.

[0051] Staining points are defined as non-cleanable, point-like attacks on the glass surface with a diameter of two µm or more.

[0052] On the atmosphere side of the soda-lime discs, five staining points of 1 mm 2 each appeared.

[0053] After these two cycles, no attacks on the glass surface of the tested borosilicate glasses were visible, neither on the tin side nor on the atmosphere side.

[0054] The distinction in the test between the tin and atmospheric side and their different results are relevant insofar as, in the case of float glass panes used as vehicle windows, the atmospheric side is preferably used as the inner side (so-called 2nd side), which is printed, for example, and the tin side as the outer side (so-called 1st side), so that for the latter, resistance to soiling such as bird droppings is of particular importance.

[0055] It is therefore a particularly preferred embodiment that the use according to the disclosure is implemented in such a way that the floated borosilicate glass pane is arranged in the installation situation in the vehicle in such a way that the side which was facing the metal bath during its hot forming is directed outwards.

Claims

1. Use of a pane as a protective pane, in particular as an outer protective pane, of a vehicle, wherein the pane comprises or consists of borosilicate glass and has a water resistance according to DIN ISO 719 / 720 of class 1 and an acid resistance according to DIN 12116:2001-03 of class 1 and passes the bird droppings simulation test.

2. Use of a disc according to claim 1, wherein within class 1 of acid resistance according to DIN 12116:2001-03 the leaching is at most 0.35 mg / dm 2 , preferably not more than 0.325 mg / dm 2 , particularly preferably not more than 0.275 mg / dm 2 and / or wherein within class 1 of water resistance according to DIN ISO 719 / 720 the leaching is at most 5 µg / g Na2O, preferably at most 4.5 µg / g Na2O.

3. Use of a disc according to claim 1 or 2, wherein the disc has a thickness between 0.5 mm and 7.5 mm, preferably a thickness between 1 mm and 4 mm, particularly preferably a thickness between 1.75 mm and 3 mm, an expansion coefficient CTE20-300 between 2.5 × 10 -6 / K and 5.2 × 10- 6 / K; preferably between 2.7 × 10 -6 / K and 5.2 × 10 -6 / K, particularly preferably between 3.0 × 10 -6 / K and 5.0 × 10 -6 / K, most preferably (3.3 ± 0.1) × 10 -6 / K and a basis weight (d1) of less than 2.25 kg / m 2 , preferably not more than 2.23 kg / m 2 , has.

4. Use of a disc according to one of claims 1 to 3, characterized in thatit comprises in wt.% on an oxide basis SiO2 70 - 87 B2O3 7 - 25 Na2O + K2O 0.5 - 9 Al2O3 0 - 7 CaO 0 - 3 MgO 0 - 2 or SiO2 70 - 86 Al2O3 0 - 5 B2O3 9.0 - 25 Na2O 0.5 - 5.0 K2O 0 - 1.0 Li2O 0 - 1.0 or SiO2 78.3 - 81.0 B2O3 9.0 - 13.0 Al2O3 3.5 - 5.3 Na2O 3.5 - 6.5 K2O 0 - 2.0 CaO 0 - 2.

0.

5. Use of a disc according to one of claims 1 to 4, characterized in that a drawing process, preferably a float process, was used as a hot forming step in their production.

6. Use of a disc according to at least one of claims 1 to 5, characterized in that the vehicle is a land vehicle, in particular a road-bound vehicle such as preferably a truck or passenger vehicle regardless of the drive, preferably with electric or hybrid drive, or a rail vehicle such as preferably a railway or tram car.

7. Use of a disc according to at least one of claims 1 to 6, characterized in thatthe pane is used as an outer protective pane in a pane composite with an inner glass pane and optionally further panes as well as with at least one, preferably polymeric, intermediate layer.

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